Tasseography is the art of tea leaf reading and, much like any other psychic fortunetelling manifestation, it's an exercise of projecting your hopes and desires into a random event; and using the pattern matching abilities of the human brain to interlucute meanings into things. In this, it's not that different from Tarot readings or Ouija boards, or even doing 'impression montages' using photographs cut out of magazines.

When brewing a cup of tea, there are objective factors which will definitely improve your results, and there are subjective factors that appeal to your personal palate. We will cover both in turn.
THE OBJECTIVE FACTORS:
The quality of the water.
The quality of the tea brewed is critically influenced by the quality of water you begin with. The best results are obtained by using filtered or purified water. High quality spring water will produce excellent results. Tap water can be suboptimal due to municipal treatments, such as added fluoride and chlorine. If you must use tap water, filter it and never use hot tap water. Hot tap water has been known to leech additional impurities from water pipes.

A new study released by the US National Library of Medicine (NLM) finds that drinking green tea can help lower blood pressure. "We investigated whether the flavonoid epigallocatechin gallate (EGCG) modulates brain activity and self-reported mood in a double-blind, placebo controlled crossover study"...